Steam generator



July 18, 1944.

G. A. REHM STEAM GENERATOR Filed May 15, 1942 2 Sheets-Sheet l G7 32 Fig.1

ATTORNEY y 1944. e. A. REHM I STEAM GENERATOR Filed May 15, 1942 2 Sheets$heet 2 gwucrvro c G USTAV A FE M Patented July 18, 1944 UNITED STATE' S TPATENT OFFICE "2,354,05 I STEAM'GENERATOR Gustav A. Rehm, Worcester, Mass, assignor to Riley Stoker Corporation, Vorces't'er', Mass, a' I corporation of Massachusetts 7 Application Mai '15 1942, Serial no. 443,03

1 Claims. (o1. zz -2.40)

. This invention relates to steam generators, and more particularly to water tube steam generators combined with superheaters and having two separate furnaces so arranged that by varying the rate of combustion in one furnace/relative to that in the other furnace the temperature of the superheated steam can be accurately con- .trolled. It is one object of the invention to provide a dual-furnace steam generatorand superheater which can be operated efliciently at relatively high rates of steam generation, with accurate control of the superheated steam temperature.

It is a further object of the invention, to provide a dual-furnace steam generator and superheater having provision for adequate water-cooling of both furnaces and so arranged that the gases from both furnaces flow in contact with suflicient convection tube surfaces to ensure comparatively high operating efficiency.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawings illustrating one embodiment of the invention, andinwhich like reference numerals indicate like parts,

Fig. 1 is a longitudinal section through a steam generator, the section being taken on the line ll of Fig. .2; and

Fig. 2 is a section on the line 2-2 of Fig. 1.

. The embodiment illustrated comprises a transverse steam-and-water drum in and a trans verse water drum ll therebeneath, these drums being connected by a rear bank of uprightwater tubes 12 and by a front bank of upright water tubes l4. In front of these tube banks there is provided a furnace or combustion chamber. l having a front wall IS with an opening I! therein for the introduction of fuel to be burned in suspension. A transverse header IQ is mounted above the furnace l5, this header being connected to the water drum H by a bank of water tubes and to the steam-and-water drum It by two rows of tubes 2|. A longitudinal lower header 23 is provided adjacent one side wall of the furnace l5, this header being connected by, water wall tubes 24 to a longitudinal upper header 25 which in turn is connected by releaser'tubes 26 to the. steam-and-water drum ID. A row of water tubes 28 extend transversely from the lower header 23 across the furnace l5 to provide a water cooled floor therefor and thence upwardly adjacent the opposite side wall to provide water wall tubes, with theirlupper ends connected to a longitudinal upper header 29 (Fig. 2), this header being connected to the steam-and-water drum ID by a row of .releaser tubes 33. Water is suppliedto the lower header 23 by a transverse header32 located adjacent the water drum H and connected to this drum by water tubes 33. The header 32 connects directly with the header 23:. Thefront wall I6 is cooled and protected by a row of watertubes 35 which extend upwardly from .alower transverse header 38 to the header I8, the-header 36 being directly connected to the header 2 3 to receive water therefrom. Iwo rows-wottubes 38 extend upwardly from the steam-and-water drum ill to a transverse steam drum 139 thereabove, the steam drum having a drain tube 40 leading downwardly outside the setting andpreferably connected to the header 23.

The gaseous products of combustion from the furnace J5 are directed into contact successively with the tubes 20, the tubes l4, and the tubes 12. For thisgpurpose a baffle 42 extends upwardly from thewater drum II behind the tubes 26, and a bafiie 43 extends downwardly from the steam-and-water. drum lflbehind the tubes l2. Between these two baffles there is provided a third orintermediate baffie 44 with its lower edge spaced .above the water drum II. This baffle 44 extends upwardly and forwardly in front of the steam-andwaterdrum l0 and in spaced rela tion therewith to provide a passage 46 through whichthe gases may escape upwardly to an offtake di -having a damper 48. With this construction the gases are compelled to flow upwardly from the furnace l5 past the tubes 2e, thence rearwardlyv over the top of the bafiie 42 and downwardly in contact with the tubes It. The gases then travel rearwardly beneath the lower edge of the baffle 44 and upwardly past the watertubes [2, past the upper portion of the tubes Hand 2|, and thence to the ofltake 45.

Behind the water tube bank 12 there is pro-- vided a second furnace having a front wall '5 l and a rear wall 52, the latter having opening'53 therein for the introduction of fuel to be burned in suspension. The front wall 51 is spaced rearwar'dly from the baffle 43 and supported by theupright intermediate portions of a row of Z-shapedwater tubes 55 which connect the water drum H with a transverse header located above the furnace 59. This header 5% is connected tov the steam-and-water drum it] by two rows of water tubes 51. The longitudinal header 23 extends rearwardly to connect with a transverse header 59 located adjacent the bottom of the rear wall 52, this wall being cooled by water wall tubes 60 which extend upwardly from the header 59 to the header 56. The side Walls and floor of the furnace50 are cooled by a tube arrangement similar to that provided for the furnace 15. Thus, side water wall tubes 6| extend upwardly from the header 23 to a longitudinal header 62 which is connected by releaser tubes 63 to the steam-and-water drum It. A row of water tubes 64 extend laterally from the header 23, in the same manner as the tubes 28, to cool the furnace floor and the opposite side Wall.

The heat produced by the combustion of fuel in the rear furnace 50 is utilized not only for steam generation but also for the superheating of steam. For this purpose a superheater 66 is located in the space or passage between the baflie 43 and the wall 5|. structed of tubes shaped to form a series of vertical loops, the inlet ends of the tubes being connected to the steam drum 39, and their outlet ends being connected to a transverse header 6'! located adjacent the bottom of the wall 5|. A row of tubes 68 extend upwardly from this header 61 in the rear of the wall 5| to a second superheater ll) likewise including vertically looped tubes, the outlet ends of these superheater tubes being connected to a transverse outlet header 'II from which the steam may be withdrawn to a place of use. The superheater I0 is located rearwardly of the superheater 66 and above the upper portions of the water tubes 55 and the furnace outlet.

In order to protect the superheater elements from excessive temperatures and from slag, I preferably provide a series of screen tubes'13 which connect the water drum l I with the header 56. These tubes 13 are Z-shaped and they extend upwardly behind the superheater tubes 68 and then rearwardly beneath the upper portions of the tubes 55.

In some cases, particularly when the steam generator is to operate at high pressures, I may provide large external downcomer tubes 15 which connect the ends of the steam-and-water drum IE) with the ends of the water drum l I. This will ensure proper water circulation at all times.

The operation of the invention will now be apparent from the above disclosure. A suitable fuel, such as oil, gas, or pulverized coal, will be burned in suspension in both furnaces. The various water tubes exposed to the radiant heat in these furnaces will generate steam rapidly, and this steam will enter the steam-and-water drum W. The gases from the front furnace 15 will flow upwardly past the tubes 20, downwardly past the tubes 14, and then upwardly past the tubes l2 and the upper portions of the tubes l4 and 2| to the ofitake 41. Any steam generated in these tubes will flow into the drum l0, where most of the water will be separated therefrom. The steam will flow from the drum l0 through the tubes 38 to the upper drum 39, where additional moisture will be separated, the steam then flowing through the superheater tubes 66, header 61, and superheater tubes 68 and 10 to the outlet header H. The gases from the rear furnace 50 will flow upwardly past the water tubes 13 and 55 into contact with the superheater 10, thence forwardly and downwardly in contact with the superheater 66 to the lower portion of the tube bank I2. At this point these gases will join the gases from the front furnace and flow upwardly This superheater is con-' therewith to the offtake 41. Thus the gases after leaving the respective furnaces take generally U-shaped paths of travel, with the upflow portions of the two paths common to both furnaces.

The front furnace l5 serves primarily as a steam generating or boiler furnace, and the rear.

furnace 50 serves primarily as a steam superheating furnace, although appreciable quantities of steam will of course be generated in the water Wall tubes of the rear furnace. By varying the rate of firing in the front furnace the steam output of the unit may be controlled, and by varying the rate of firing in the rear furnace the temperature of the superheated steam may be controlled. In general, in order to maintain a constant superheat under conditions of varying demand for steam, it will be necessary to vary the firing rates in both furnaces. This is a comparatively simple matter. After leaving the superheater 66 the gases from the rear furnace 50 are not discharged, but they must first flow past the water tubes l2 and the upper portions of the water tubes l4 and 2| before reaching the offtake 41. Thus the temperature of these gases will be decreased to a relatively low value, and the emciency of the unit will be correspondingly increased.

The terms front, rear, and the like as used in the claims appended hereto ar not to be considered as limitations except in so far as they define the relative positions of the various parts.

Having thus described my invention, what l claim as new and desire to secure by Letters Patent is:

1. A steam generator comprising a transverse steam-and-water drum, a transverse water drum therebeneath, a bank of upright water tubes connecting the drums, a baffle located in front of the tube bank, a rear baffie located behind the tube bank, the lower edges of both baffles being spaced from the water drum, and the upper portion of one baflle being spaced from the steamand-water drum to provide a gas passage, an ofitake connected with the said gas passage, a steam generating furnace spaced forwardly from the first-mentioned baffle and having an outlet in its upper portion, means to conduct hot gases from the outlet downwardly in front of the firstmentioned baffle and rearwardly beneath the lower edge thereof, a superheater furnace spaced rearwardly from the rear baflle and having an outlet in its upper portion, a superheater located between the superheater furnace and the tube bank, means to conduct hot gases from the superheater furnace outlet into contact with the superheater and downwardly behind the rear baflle and thence forwardly beneath the lower edge thereof, and means to conduct the gases from both furnaces upwardly in contact with the tube bank to the offtake.

- 2. A steam generator comprising a transverse steam-and-water drum, a transverse water drum therebeneath, a bank of upright water tubes connecting the drums, a baffle located in front of the tube bank with its lower edge spaced above the water drum and its upper portion spaced forwardly from the steam-and-water drum, a steam generating furnace spaced forwardly from the baffle and having an outlet in'its upper portion, means to conduct hot gases from the outlet downwardly in front of the baflie and rearwardly beneath the lower edge thereof, a superheater furnace in the rear of the tube bank and having an outlet in its upper portion, a superheater located between the superheater furnace and the tube 3; A steam generator comprising a transverse steam-and-water drum, a transverse water drum therebeneath, front and rear banks of upright Water tubes connecting the drums, a rear 'bafile extending downwardly from the steam-and-water drum behind the rear tube bank, a front baffle extending upwardly from the water drum in front of the front bank, and intermediate baflle between the front and rear battles with its upper portion spaced forwardly from the steam-andwater drum, an oiftake connected with the space between the intermediate baffle and the steamand-water drum, the lower edges of the rear and intermediate bafiles being spaced from the water drum, a steam generating furnace in front of the front baffle having an outlet in its upper portion, the hot gases from theoutlet flowing rearwardly and downwardly between the front and intermediate baffles and beneath the lower edge of the intermediate baffle, a superheater furnace behind the rear bafile and having an outlet in its upper portion, a superheater located between the superheater furnace and the rear baflle, means to conduct hot gases from the superheater furnace outlet into contact with the superheater and downwardly and forwardly beneath the lower edge of the rear bafile to mix with the gases from the steam generating furnace, and means to conduct the mixed gases upwardly in contact with the rear tube bank and to the offtake.

4. A steam generator comprising a transverse steam-and-water drum, a transverse water drum therebeneath, a bank of upright water tubes connecting the drums, a bafile in front of the tube bank with its lower edge spaced from the water drum and its upper portion spaced forwardly from the steam-and-water drum, an olftake connected with the space between the baffle and the steamand-water drum, a rear baffle extending downwardly from the steam-and-water drum with its lower edge spaced from the water drum, a steam generating furnace in front of the tube bank having an outlet in its upper portion from which hot gases flow downwardly and rearwardly beneath the lower edge of the first-mentioned baffle, a superheater furnace behind the tube bank and having an outlet in its upper portion, the superheater furnace having a front wall which is spaced rearwardly from the rear baffle, a superheater located in the space between the said front wall and the rear baffle, the hot gases from the superheater furnace outlet flowing downwardly in contact with the superheater and forwardly beneath the rear baflle to mix with the gases from the steam generating furnace, and means to conduct the mixed gases upwardly in contact with the tube bank and to the ofitake.

5. A steam generator comprising a transverse steam-and-water drum, a transverse water drum therebeneath, a bank of upright water tubes connecting the drums, a baflle in front of the tube bank with its lower edge spaced from the water drum and its upper portion spaced forwardly from the steam-and-water drum, an offtake connected with the space between the baffle and the steamand-water drum, a rear baffle extending downwardly from the steam-and-water drum with its lower-'edge'spaced from the water drum, a steam generating furnace in front of the tube bank having-an outlet-in'its upper portion from which hot gases flow downwardly and rearwardly beneath the lower edge of the first-mentioned baflle, a superheater furnace behind the tube bank and having an outlet in its upper portion, the superheaterfurnace having a front wall which isspaced rearwardly fromthe rear 'baflle, a transverse headerabov'e the superheater furnace, tubes connecting the header with the steam and-water drumfia row of z-sha'ped' water tubes connecting the water drum with the'header and having upright intermediate portions arranged to support and cool the said front wall, a superheater located in the space between the said front wall and the rear baffle, the hot gases from the superheater furnace outlet flowing downwardly in contact with the superheater and forwardly beneath the rear bafiie to mix with the gases from the steam generating furnace, and means to conduct the mixed gases upwardly in contact with the tube bank and to the oiftake.

6. A steam generator comprising a transverse steam-and-water drum, a transverse water drum therebeneath, a bank of upright water tubes connecting the drums, a battle in front of the tube F a steam generating furnace in front of the tube bank having an outlet in its upper portion from which hot gases flow downwardly and rearwardly beneath the lower edge of the first-mentioned baffle, a superheater furnace behind the tube bank and having an outlet in its upper portion, the superheater furnace having a front wall which is spaced rearwardly from the rear baflle, a transverse-header adjacent the lower portion of the front wall, superheater tubes located in front of the front wall with their discharge ends connected to the header, a superheater located above the outlet of the superheater furnace, tubes extending upwardly from the header and along the rear face of the front wall to the superheater, the hot gases from the superheater furnace outlet flowing in contact with the superheater and the superheater tubes and then forwardly beneath therear baffle to mix with the gases from the steam generating furnace, and means to conduct the mixed gases upwardly in contact with the tube bank and to the offtake.

'7. A steam generator comprising a transverse steam-and-water drum, a transverse water drum therebeneath, a bank of upright water tubes connecting the drum, a baflle in front of the tube bank with its lower edge spaced from the water drum and its upper portion spaced forwardly from the steam-and-water drum, an offtake connected with the space between the baille and the steamand-water drum, a rear baffle extending downwardly from the steam-and-water drum with its lower edge spaced from the water drum, a steam generating furnace in front of the tube bank having an outlet in its upper portion from which hot gases flow downwardly and rearwardly beneath the lower edge of the first-mentioned bafile, a superheater furnace behind the tube bank and having an outlet in its upper portion, the superheater furnace having a front wall which is spaced rearwardly from the rear baffle, a transverse water header above the superheater furnace behind the outlet thereof, tubes connecting the header with the steam-and-water drum, a row of Z-shaped tubes connecting the water drum with the header and having upright intermediate portions arranged to support and cool the said front wall, a transverse steam header adjacent the lower portion of the front wall, superheater tubes located in front of the front Wall with their discharge ends connected to the header, a superheater located above the outlet of the superheater furnace, tubes extending upwardly from the steam header and along the rear face of the front wall to the superheater, a row of Z-shaped tubes connecting the water drum with the water header and having upright intermediate portions located behind the last-mentioned tubes to protect them from excessive radiant heat, the hot gases from the superheater furnace outlet flowing in contact with the superheater and the superheater tubes and then forwardly beneath the rear bafile to mix with the gases from the steam generating furnace, and means to conduct the mixed gases upwardly in contact with the tube bank and to the ofitake.

GUSTAV A. REHM. 

